RU2780562C1 - Method for preparing potassium iodate from potassium iodide - Google Patents

Abstract

FIELD: inorganic substances chemical technology.

SUBSTANCE: invention relates to the field of chemical technology of inorganic substances, and in particular to a method for producing potassium iodate used in the pharmaceutical and chemical industries. A method for producing potassium iodate from potassium iodide is proposed, including the oxidation of iodide ion with an ozone-air mixture, characterized in that the oxidation of potassium iodide is carried out in an aqueous solution of potassium hydroxide, the resulting molecular iodine disproportionates into potassium iodate and potassium iodide, which again enters into oxidation process, after complete oxidation of iodide ions, the solution is cooled to 5°C, separated by filtration separated crystals of potassium iodate and washed with distilled water at a temperature of 1-5°C.

EFFECT: method makes it possible to simplify the technology for obtaining potassium iodate while refusing electrochemical methods and environmentally unsafe oxidizing agents, as well as to increase the yield of the target product.

4 cl, 1 tbl

Description

The invention relates to the field of chemical technology of inorganic substances, and in particular to a method for producing potassium iodate used in the pharmaceutical and chemical industries.

Known methods of electrochemical oxidation of potassium iodite to potassium iodate in an aqueous solution on graphite anodes at a current density of 100-300 A/m ² and a temperature of 60-95°C [SU 865983, SU 1096307] in the presence of potassium bichromate. Their advantage is the absence of particularly dangerous reagents for oxidation, high current efficiency of potassium iodate, and simple control of the oxidation process.

A known method for producing potassium iodate, proposed by the authors of patent RU 2210533 C1, based on the interaction of iodine with potassium hydroxide, with the formation of iodite and potassium iodate in the reaction mass at an alkalinity of up to 8 kg/m ³ , the content of iodite ions up to 160 kg/m ³ and iodate ions up to 50 kg / m ³ . The mass is subjected to electrolysis followed by evaporation at a temperature of at least 80°C for pre-crystallization and crystallization upon cooling. The disadvantages of this method are the high time spent on filling the cell and draining the solution from the cell, high energy consumption during the evaporation of the solution before crystallization of potassium iodate. And also, when carrying out intensive crystallization of potassium iodate to prevent co-precipitation of potassium iodite, it is necessary to maintain a low concentration of potassium iodite in the mother liquor. Oxidation of potassium iodite to a concentration close to zero leads to a decrease in current strength and current efficiency of potassium iodate, and increases the electrolysis time. Maintaining the current strength requires an increase in the input voltage, but at low concentrations of iodite in the solution, the wear of the anodes increases and the time of their operation decreases.

Known methods for producing potassium iodate, based on the oxidation of iodine or potassium iodite with oxidizing agents, such as Berthollet salt, chlorine, bromine in an acidic or neutral environment [V.I. Ksenzenko, D.S. Stasinevich. Chemistry and technology of bromine, iodine and their compounds. - M.: Chemistry, 1995, 432 s, Remy. Course of inorganic chemistry. T. 1. - M.: Mir, 1972, p. 777]. The disadvantage of these methods is the use of high concentrations of highly hazardous oxidizing agents, high consumption of reagents, the need to dispose of reaction by-products, special corrosion-resistant equipment and safety equipment for the storage and use of oxidizing agents.

Closest to the proposed method for producing potassium iodate is a method for producing iodine based on the oxidation of iodite ion using ozone, and carried out in an acidic environment at pH 2.5 - 3 [Ksenzenko V.I., Stasinevich D.S. // Chemistry and technology of bromine, iodine and their compounds. M .: Chemistry, 1995, p. 300., Auth. certificate RF 66684, 12i9, Appl. 18.05.45.]. The disadvantage of the prototype is the low yield of iodine - up to 85% of theoretical, the impossibility of obtaining potassium iodate due to the low acidity of the medium.

The similarity of the proposed method and the prototype lies in the use of ozone as an oxidizing agent.

The technical objective of the invention is the simplification of the technology for obtaining potassium iodate, the exclusion of electrolysis processes, the rejection of the use of highly toxic oxidizing agents and the increase in the yield of the target product - potassium iodate.

The result of the invention is the simplification of the technology for obtaining potassium iodate while refusing electrochemical methods for producing potassium iodate, as well as environmentally unsafe oxidizers.

This result is achieved by the fact that in the proposed method, potassium iodite, dissolved in an aqueous solution of potassium hydroxide, is oxidized by an ozone-air mixture. The resulting molecular iodine disproportionates into potassium iodate and potassium iodite, which again enters the oxidation process. The resulting potassium iodate, having low solubility in aqueous solutions, precipitates and is removed from the reaction medium. The output of potassium iodate reaches 99% of the theoretical, based on the original iodine.

The method is carried out as follows.

A solution of potassium iodite in an aqueous solution of potassium hydroxide (content of potassium iodite 0.5 - 12 g/100 g of solution, potassium hydroxide 10 - 35 g/100 g of solution) is treated with an ozone-air mixture flow. The ozone content in the ozone-air mixture is 0.1 - 10 mg/l. The consumption of ozone is 100 - 120% of the stoichiometric in relation to the iodite ion. The consumption of the ozone-air mixture is determined by gas volumetrics.

After complete oxidation of iodite ions, the solution is cooled to 5°C and separated by filtration separated crystals of potassium iodate and washed with distilled water at a temperature of 1-5°C.

The precipitate of potassium iodate can be removed from the reaction vessel as it accumulates.

Specific conditions for implementing the method may vary.

Examples confirming the possibility of obtaining potassium iodate by the proposed method are shown in table 1.

The content of potassium iodate was determined in the absorption solution by iodometry. The saturated reaction solution was also tested for the presence of molecular iodine and iodite ion. The presence of molecular iodine and iodite ion in the solution was not detected during confirmatory experiments, iodite ion was completely oxidized to iodate ion.

From the above examples it can be seen that the proposed method is possible to obtain potassium iodate with a yield of up to 99%.

To implement the proposed method, standard equipment used in chemical technology can be used.

The inventive method is environmentally friendly, because. the resulting product does not contain organic solvents, and the process does not produce toxic or hard-to-dispose waste or by-products.

The inventive method can be used to obtain potassium iodate, both in laboratory practice and in industry, and is suitable for both periodic and continuous technological methods.

Process for producing potassium iodate from potassium iodite

Table 1. Examples confirming the possibility of implementing a method for producing potassium iodate from potassium iodite No./No. example Content of potassium iodite, g/100g of solution The content of potassium hydroxide, g / 100 g of solution Ozone content in OWS*, mg/l Ozna consumption, % of stoichiometric Method for removing accumulated potassium iodate** Yield of potassium iodate, % of theoretical one 0.5 ten 0.1 100 one 99.9 2 5 twenty 7.5 110 one 99.9 3 ten thirty 5 120 2 99.9 four 12 35 ten 120 2 99.9 5 one fifteen 0.5 100 2 99.9 6 7.5 thirty one 110 one 99.9

* OVS - ozone-air mixture.

** Method for removing accumulated potassium iodate: 1 - after complete oxidation of potassium iodite; 2 - periodically during accumulation in the reaction medium.

Claims (4)

1. A method for producing potassium iodate from potassium iodide, including the oxidation of iodide ion with an ozone-air mixture, characterized in that the oxidation of potassium iodide is carried out in an aqueous solution of potassium hydroxide, the resulting molecular iodine disproportionates into potassium iodate and potassium iodide, which re-enters in the oxidation process, after the complete oxidation of iodide ions, the solution is cooled to 5 °C, the precipitated potassium iodate crystals are separated by filtration and washed with distilled water at a temperature of 1-5 °C. 2. The method according to p. 1, characterized in that the content of potassium iodide is 0.5-12 g/100 g of solution. 3. The method according to p. 1, characterized in that the content of potassium hydroxide is 10-35 g/100 g of solution. 4. The method according to p. 1, characterized in that the ozone content in the ozone-air mixture is 0.1–10 mg/l.